The invention relates to a fastening element which can be connected to a component. In particular, the invention relates to a T-stud or a punch (or self-piercing) rivet with a short shank. The invention also relates to a device for feeding a fastening element to a fastening position in which it can be fastened on or in a component. The feeder has a loading duct and a loading pin capable of reciprocating in the loading duct. The fastening element is pushed into the fastening position by a movement of the loading pin.
A fastening element designed as a weld stud is known, for example, from U.S. Pat. No. 4,799,842, wherein the weld stud has a cylindrical region to be grasped by a stud-welding device which is adjoined by a threaded shank of smaller diameter. The cylindrical region to be grasped by the stud-welding device is relatively narrow, so that there is a risk, as the stud is being fed to a fastening position in which the stud is welded, that the weld stud will not be fed in the correct orientation, for example will not be fed with its fastening end first.
A feeder for in particular elongate fastening elements designed, with a head, is described in U.S. Pat. No. 5,588,576. The feeder has clamping tongs with at least two clamping arms, the clamping arms having a guide step for guiding the elongate fastening element and a recess adapted to the external shape of the elongate components to be clamped. Jamming or tilting of the fastening elements to be fed is avoided in this way, in particular at high feed rates.
U.S. Pat. No. 5,695,045 describes a stud feeder comprising a loading duct with a stud feed orifice designed substantially perpendicularly to the loading duct and a loading pin capable of reciprocating in the loading duct. A stud to be fed is shifted from the stud feed orifice to a stud holder by the loading pin. The loading duct is designed in the form of tubular tongs which are slotted at least over a proportion of their length and of which the tong segments separated from one another by the slots are resiliently substantially perpendicularly to the length. Secure, reliable positioning of the stud in the stud holder is therefore achieved, in particular also in the case of T-studs with a short shank the shank length of which is smaller than the head diameter.
U.S. patent application Ser. No. 08/941,923 now U.S. Pat. No. 6,015,962, also discloses a stud welding device with stud feeder, of the welding gun type. The loading duct of the stud feeder has, at an outlet aperture, a stud holder with resilient holding fingers. A stud can be held and guided in the correct position by the stud holder both during the feed process and during the subsequent welding process.
It is an object of the present invention to provide a fastening element and a device for supplying the fastening element to a fastening position which ensures reliable positionally correct feeding of the fastening element into the fastening position.
The present invention provides a fastening element for fastening on or in a component, in particular T-stud or punch rivet, with a fastening end, characterised in that the fastening element has, at a guide end remote from the fastening end, a recess for receiving a tool end piece which fits into the recess and by means of which the fastening element can be positioned.
The present invention further provides a device for supplying a fastening element into a fastening position in which the fastening element can be fastened on or in a component, with a loading duct and a loading pin capable of reciprocating in the loading duct, characterised in that the loading pin has a tool end piece fitting into the recess such that the fastening element can be guided positionally correctly into the fastening position.
The fastening element according to the invention has, at a guide end remote from the fastening end, a recess for receiving a tool end piece fitting into the recess. If the fastening element is guided into the fastening position by means of a suitable tool, there is at most a limited possibility that the fastening element will adopt a position different from the proposed position. The tool can therefore be guided rigidly or can be guided flexibly to a certain extent so it can follow possible movements of the fastening element from the proposed position to a desired limit. In either case, the fastening element will maintain engagement with the tool end piece in the region of the recess and will not be able to deviate further than from the maximum deviation in position.
In a development of the fastening element according to the invention, the fastening element is a so-called T-stud or a punch rivet with a shank and a head connected to the shank, the head having a greater cross-sectional area than the shank and the head forming the guide end with the recess.
In a further development, the length of the fastening element, measured between the fastening end and the guide end, is smaller than or equal to the width of the fastening element, measured perpendicularly to the longitudinal direction, i.e. to the direction in which the length is measured. Fastening elements of such a design deviate from the correct position particularly easily during the feed process if they are fed longitudinally in a feed duct. This can reliably be avoided with the design, according to the invention, of a recess at the guide end.
For many applications it is desirable if the external contour is substantially symmetrical with respect to a longitudinal axis of the fastening element, the recess also being substantially symmetrical with respect to the longitudinal axis.
In an advantageous design of the fastening element, the recess tapers from the guide end toward the fastening end, i.e. the cross-sectional area of the recess diminishes. An advantage of this design is that the tool end piece can be reliably introduced into the recess even if the fastening element is not in exactly the correct position. A further advantage is that a fastening element is correctly orientated if it is guided laterally along a guide by means of the tool end piece.
The cross-sectional area of the recess can be, for example, polygonal or circular. With a circular design, a tool end piece which is also circular in cross section is preferably used. The tool end piece can be introduced into the recess without axial rotation. In certain circumstances, the fastening element is to be fed in a specific rotational position with respect to a longitudinal axis. A recess having a polygonal cross-sectional area is advantageous in such cases.
The feeder according to the invention has a loading duct, in which a fastening element according to the invention can be guided into a fastening position, and a loading pin capable of reciprocating in the loading duct. The loading pin has a tool end piece fitting into the recess so that the fastening element can be guided positionally correctly into the fastening position. The fastening element is preferably introduced into the loading duct by an elastic tube the internal cross section of which corresponds substantially to the longitudinal section of the fastening element. The loading pin travels from a retracted position with the tool end piece first onto the guide end of the positionally substantially correctly orientated fastening element and engages in the recess with the tool end piece. The fastening element is guided in the loading duct to the fastening position by continued movement of the loading pin.
Like known feeders, the feeder according to the invention can be designed with a loading duct and a loading pin but with the difference that the loading pin has the tool end piece. Reference is made to the content of U.S. patent application Ser. No. 08/941,923 and U.S. Pat. No. 5,695,045 for details of such feeders.
In a development of the feeder, the tool end piece fits positively into the recess at the guide end of the fastening element. An advantage of this design is that the fastening element can be supplied with play which is not or is only insignificantly greater than the play with which the loading pin is moved in the loading duct.
In a further design, the loading pin has a base portion the cross-sectional area of which is greater than the cross-sectional area of the tool end piece so that the base portion can be brought to rest on the guide end of the fastening element outside the recess. An advantage of this design is that, in particular, T-studs or punch rivets with a short shank can be fed particularly reliably into the correct position.